1. Field of the Invention
The present invention relates to a musical tone waveform signal forming apparatus utilized as a sound source of electronic musical instruments, music education apparatuses, toys, and the like and, more particularly, to a musical tone waveform signal forming apparatus for receiving a musical tone control signal for steadily or time-serially controlling musical tone parameters such as a pitch, a tone color, a tone volume, and the like of a musical tone, and forming a musical tone waveform signal according to the input musical tone control signal.
2. Description of the Prior Art
As an apparatus of this type, an apparatus which utilizes a so-called delay feedback type decay tone algorithm for inputting a nonlinear signal to a delay loop system including a delay circuit to perform feedback arithmetic processing, thereby forming a musical tone signal (to be referred to as a delay feedback type musical tone waveform signal forming apparatus hereinafter) is known (for example, Japanese Patent Laid-Open No. Sho 63-40199).
The delay feedback type musical tone waveform signal forming apparatus physically approximates mechanical vibration systems of acoustic instruments such as strings of a bowed instrument, a tube body of a wind instrument, and the like by means of an electrical circuit. This apparatus is expected to be able to relatively naturally and faithfully synthesize a tone of a bowed instrument or wind instrument as well as a change in tone level by inputting a nonlinear signal corresponding to a movement of a contact between a bow and a string of a bowed instrument or a reed or an embouchure of a wind instrument to the delay loop.
However, a delay feedback type musical tone waveform signal forming apparatus which can reproduce a musical tone added with a vibrato effect to have high fidelity to an acoustic instrument has not been realized yet.